A synchronous pulse width modulation (PWM) signal for driving a switching element configuring an inverter is often generated by a PWM system. The PWM system is a system for appropriately controlling ratios of an ON time and an OFF time to a switching period, which is a specific time, to thereby output, as an average voltage in the switching period, a voltage that the switching element is capable of instantaneously outputting, that is, a voltage between a collector-emitter applied voltage and a zero voltage.
Patent Literature 1 discloses a driving control device that corrects, in over-modulation PWM control, voltage command amplitude on the basis of a synchronous number K using different voltage amplitude characteristic maps to thereby prevent fundamental wave amplitude of a pulse width modulation voltage applied to a motor from changing because the synchronous number K changes.